The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Powertrain systems may be configured to transmit torque originating from plural torque generative devices, e.g., internal combustion engines and non-combustion torque machines, through a transmission device to an output member that may be coupled to a driveline. Such powertrain systems include hybrid powertrain systems and extended-range electric vehicle systems. Control systems for operating such powertrain systems operate the torque-generative devices and apply torque transfer elements in the transmission to transfer torque in response to operator-commanded output torque requests, taking into account fuel economy, emissions, driveability, and other factors. The non-combustion torque machines may include electric machines that are operative as motors or generators to generate a torque input to the transmission independently of a torque input from the internal combustion engine. The torque machines may transform vehicle kinetic energy, transferred through the vehicle driveline, to electrical energy that is storable in an electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling transmission operating state and gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage outputs of the transmission, including torque and rotational speed.
Such powertrain systems may include control systems that execute autostop and autostart control schemes to turn the internal combustion engine on and off during ongoing operation. During an engine start, compression torque pulses are generated in individual engine cylinders and transmitted to a transmission torque damper and an engine block, which may result in objectionable vibrations reaching the vehicle operator, especially at resonant frequencies for the powertrain and various driveline components. The compression torque pulses can disturb engine output torque and can result in objectionable physical vibration and audible noise.